The present invention relates to disposable absorbent articles, such as incontinence garments for infants, children, and adults, including disposable underwear, disposable diapers, disposable pull-on diapers, disposable training pants, and disposable panties for menstrual use. More specifically, the present invention relates to disposable absorbent articles that include retention zones for preventing slippage of the absorbent article relative to the body of a wearer during the time the article is worn.
Infants and others who are incontinent wear disposable absorbent articles such as diapers or other absorbent undergarments to receive and contain urine and other bodily exudates. Absorbent articles in the form of garments that are pre-assembled for slip-on application on the body of a wearer (e.g., training pants or pull-on diapers) have recently become popular. In order both to contain bodily exudates and also to fit a wide variety of body shapes and sizes, such garments must fit snugly about the waist and legs of the wearer without drooping, sagging, or sliding down from their position on the lower torso, and without causing unnecessary pressure on the skin by reason of the product being too tight for the wearer's comfort.
Many types of pull-on garments use conventional elastic elements secured in an elastically contractible condition in the waist and leg openings. For example, pull-on absorbent garments known as “balloon type” pants include elasticized bands in specific zones of the product that are in contracted form, while the remaining material tends to blouse. Examples of such pull-on garments are disclosed in U.S. Pat. No. 5,171,239 published on Dec. 15, 1992, U.S. Pat. No. 4,610,681 published on Sep. 9, 1986. Those garments will fit a range of waist and leg sizes because the elastic portions will expand to accommodate various size wearers. Nonetheless, the range of sizes is limited because the elastic elements, which enable this variation in size, have a limited degree of stretch. The narrow elastic bands used in the waist opening and the leg openings also tend to concentrate the fit forces in a narrow zone of the wearer's body leading to increased incidence of skin marking of the wearer.
Other types of pull-on, absorbent garments that employ waist elastics and side elastics are disclosed in U.S. Pat. No. 4,940,464, published on Jul. 10, 1990, U.S. Pat. No. 5,246,433, published on Sep. 21, 1993, U.S. Pat. No. 5,591,155, published on Jan. 7, 1997, EP publication 0 526 868 Al published on Feb. 10, 1993, U.S. Pat. No. 5,545,158 published on Aug. 13, 1996; and EP publication 0 547 497 A2, published on Jun. 23, 1993.
Disposable, absorbent garments of the type identified above are generally held in position on the body of the wearer by an elasticized structure that is positioned in the waist area of the garment. The elasticized structure is preferably under tension to generate a hoop stress within the waist structure and cause it to engage with and to press against the waist area of the wearer. And to minimize downward slippage or drooping of such garments while they are worn, the hoop stress within the elasticized waist structure must be large enough to cause an inward force of sufficient magnitude to press against the skin at the wearer's waist The inward force should be great enough to provide a normal force against the wearer's body to result in sufficient friction between the wearer's skin and the inner surface of the elastic waist structure to overcome those forces that act to tend to pull the garment down from the wearer's waist, away from garment's initial position when it was first applied to the wearer. In that regard, the downward forces acting on the garment to pull it down are caused, in part, by movements by the wearer, and they are also caused, in part, by an increase in the weight of the absorbent, exudate-receiving core, which results from the absorption and containment by the absorbent core of waste products in the form of urine and fecal material.
But in providing sufficient hoop stress within the elasticized waist structure to attempt to cause the garment to be retained in its initial position on the wearer's body, the inward force acting against the wearer's waist causes pressure and tightness to be exerted on the body of the wearer, which can cause wearer discomfort, and can also cause undesirable pressure marks, sometimes referred to as “red marks,” on the wearer's skin about the wearer's waist. Such red marks are indicative of the relatively high inward forces that are imposed on the wearer's waist, and they are undesirable both because they cause discomfort to the wearer and also because they cause anxiety to mothers of small children who wear such garments. The present invention is directed to minimizing such discomfort and the attendant red marking of the wearer's skin by providing increased surface static friction between the garment and the wearer's skin, which enables the hoop stress, and the resulting inward forces acting against the wearer's body, to be reduced. Additionally, because it enables lower pressure forces against the skin of a wearer, the present invention also serves to reduce skin abrasion resulting from relative movement of portions of such garments and the wearer's skin.
The broad notion of increasing the coefficient of friction of an interior surface of a disposable diaper is disclosed in U.S. Pat. No. 5,782,819, entitled “Article with Stay-In-Place Feature,” which issued on Jul. 21, 1998, to Tanzer et al., and in International Patent Publication No. WO 95/22306, entitled “Absorbent Pant Diaper,” which was published on Aug. 24, 1995, in the name of Kling et al. as inventors. However, the latter does not disclose particular values of coefficient of friction, and it teaches placement of a friction agent at the hip portions of the diaper, but not over the side seams and not in the back portions of the diaper. And the former discloses an arrangement wherein the dynamic coefficient of friction has a first value when movement occurs in a first direction, and a second value when movement occurs in the opposite direction.
It is an object of the present invention to provide a disposable absorbent article that includes a relatively high coefficient of static friction at selected portions of the skin-facing surfaces of the article, to retain the article in its desired wearing position during movements by the wearer.
It is another object of the present invention to provide a disposable absorbent article that includes a relatively low coefficient of static friction on selected portions of the structure to facilitate application of the article to the body of a wearer and also to facilitate removal therefrom.